Means for controlling aeroplanes when in flight



1 ch 15, 19%. H, L, PITT 2,111,481

MEANS FOR CONTROLLING AEROPLANES WHEN IN FLIGHT Filed Dec. 3, 1936 3 Sheets-Sheet l 6 Fig.1.

mms/vra/r 7/2/56/211 FIZZ,

, H. L. PITT 2,111,481

MEANS FOR CONTROLLING AEROPLANES WHEN IN FLIGHT I Filed Dec. 3, 1956 3 Sheets-Sheet 2 March 15, 1938. PITT 2,111,481

PQEANS FOR CONTROLLING AEROPLANES WHEN IN FL IGHT Filed Dec. 3, 1936 r 3 Sheets-Sheet 3 isles ra'rsu'r iiFiil MEANS FOR CONTROLLING AEROPLANES WHEN IN FLIGHT Hubert Lewellen Pitt, Westclifie-on-Sea, England Application December 3, 1936, Serial No. 114,084 In Great Britain October '7, 1935 10 Claims. (Cl. 244-42) In known aircraft, directional and lateral conat the wing tip and negative pressure or an introl is achieved by the use of one or more vertical crease of lift, according to the degree of openrudders and ailerons hinged on the wings and ing of the orifice by the control surface and the acting in opposite directions to each other; that relative velocity of the airstream caused to flow is to say, when one aileron is up the other is through the orifice and past the control surface, down. These two control surfaces have to be and thereby effecting a redistribution of pressure correlated, bythe skill of the pilot, in order to between the lower and upper wing surfaces achieve correct turn and bank. Further, the through the orifice in which the control surface drag caused by the ailerons is greatest on that is disposed.

10 wing which, being at the outside of the circular The said an Wh c the aXiS 0f the trol 10 path is travelling the faster, thereby inefficiently Su face makes With t e o tudinal axis of the resisting the desired motion, and causing a aircraft is measured from the longitudinal axis tendency for the aeroplane to spin at or near outwards towards the front of the aircraft.

the stalling point, These disadvantages are The term SOIid used above in connection with present in aeroplanes with or without tails, if the construction of the control surface means 15 having the usual control surfaces. that there is no passage for the air to flow A prior proposal h b d t t t, through the control surface and that the'air is ea h wing of an aeroplane of an Outer frame, forced to flow over the upper and lower surfaces an inner frame and a single surface within the 0f e o t Surface. The term does not, of

inner frame, the construction being such that Course, eXelude a Control Surface having a hollow th inner frame nd single surface could b interior. Reference is made. above to the con- 20 turned in om n b t an i t right angle trol surface not being greater in area than half to the longitudinal axis of the aeroplane. The h r of he Win In the case of a continuinner frame and single surface together form the 0115 Wing not interrupted y the fuselage the major ti f th i expression area of the wing means the area 25 The disadvantage of any arrangement in of that portion of the wing projecting outwards which a control surface is pivoted in an orifice 011 the p Starboard Side as the c y he in a wing with its axis either t a right, angle beyond the adjacent outer surface or the level of to the longitudinal axis of the aeroplane or parthe a jac nt outer rf of th fu l e.

allel thereto is that forces will be produced which n the Control Surface Opens the Orifice 30 will act with much greater effect about one parthrough t e W it is adapted to Cause a rearticular axis than about another, ward flow of the airstream from the high pres- To overcome all the above mentioned disadsure area beneath h l n e o the low vantages, according to the present invention I pressure area above the win so that W ve provide an aeroplane comprising control surfaces, y e t e o w d and d W WMd Ve ty of each of which is not greater in area than half e aircraft the V y of the air fiOW through the area of the wing and is mounted in an the orifice and, therefore, in front and behind orifice formed in the wing between the leading h n r surface, m be at least as great or and trailing edges of the latter, the control surr er s n e pr s r q li ti n Will acceler- 40 face being solid in construction and adapted to e t e ow from high to low pressure This 0 be turned relatively to said orifice on an axis ns r s that the W rse tendency f r the wine which is directed forwardly and inclined to the o st the o e t ihelihetieh for this P longitudinal axis of the aircraft at an angle sure equalization to check all potential oscillawhich is less than 90 to said axis, said control tion about any axis even in vertical descent.

i5 surface also being so constructed and arranged The said control surfaces have therefore as their that when turned from its inoperative position, main object the simplified and safe control of its leading edge projects downwards and forthe aeroplane, which is thus rendered substanwards towards the leading edge of the wing tially fool proof and enabled to descend and whilst its trailing edge projects upwards and ascend at an angle of flight path much steeper o0 rearwards; whereby air from the underside of than would otherwise be possible. Thus the the wing is caused to flow both over the top suraeroplane can enter a very confined space almost face and over the underside of the control survertically under complete and unskilled control. face rearwards or mainly rearwards and up- When both movable surfaces are actuated in wards through the orifice in the wing, thereby unison, the effect is to cause a tendency for the causing either a destruction of lift, pressure loss rear portions of the wing, which are behind the centre of gravity of the aeroplane, to drop, thus creating an increase in the real angle of attack, and to increase the sinking speed, whereby the true angle of descent or glide can be varied without danger of stalling. Further, the profile drag and the induced drag caused by the air-brake action of the control surface and the boundary layer separation when the control surfaces are in the raised position creates additional drag and reduces the landing speed. In addition, the true angle of attack of the wings and the landing speed can be increased and decreased, respectively, at the moment before the aeroplane contacts with the ground, although, nevertheless, the aeroplane still maintains a horizontal, or approximately horizontal, attitude about the lateral axis at whatever angle of attack or sinking speed.

When the control surfaces are operated independently, the drag and loss of lift occur on one wing only and this, together with the turning moment caused by the angle of inclination of the axis of the movable control surface to the flight path causes the desired directional control with the required bank. If the axis of the movable control surface is such as to constitute a fully or partially balanced surface and the lower part projects through and below the wing, the down pressures of the air acting on that part of the surface which sinks through the wing when the control surface is operative tend to reduce the operating loads for the control surface and are therefore advantageous. In a turn and bank, therefore, the five factors which come into operation are loss of lift, induced drag, profile drag, turning moment and down pressure on the control surface, and all these forces act on the inner wing only.

The control surfaces can be actuated by one operating means only (e, g. a steering wheel) and each surface performs the complete function of two control surfaces on known aeroplanes, viz. ailerons and rudder, and part of the function of the elevator, in so far as variation in glide and attack angle at landing is concerned.

The movable control surfaces may be so constructed and arranged that when the surfaces are in their inoperative positions, part or the whole of their upper and lower surfaces form part of the profile curvature of the upper and lower wing surface, respectively, although the said upper and lower surfaces could also be above or below the wing surfaces. The control surfaces are preferably nicely accommodated in orifices formed in the wings. When a control surface is in its operative position, the leading part thereof will project downwardly out of the orifice in the wing whilst its trailing part will project upwardly out of said orifice.

In plan view, the control surfaces may be of many shapes. For example, they may be pearshaped, with their smaller ends directed towards the leading edges. The said surfaces may be hinged on a central or noncentral axis and may be fully or partially balanced, the said axis being arranged preferably between to to the line of flight or central axis fore and aft. section, said surfaces may conform to the cross section of that part of the wing in which they are fitted. If the control surfaces are centrally hinged or fully balanced, the forward part of a surface could be made to expose an orifice in the wing as it descended below the surface and thus be subject to down pressure whilst the other half of the surface would rise so as to present a de- In crossfleeting surface towards the Wing tip. As mentioned above, the area of the control should not be greater than half that of the wing and probably about one-third will be the maximum proportion, although this will depend upon individual requirements.

The control surfaces can be connected by means of suitable mechanism to a steering wheel, for example, in such manner that each of the surfaces can be operated independently or both simultaneously, as desired.

Several constructional forms of the invention are shown diagrammatically and by way of example on the accompanying sheets of drawings, whereonz- Fig. 1 is a fragmentary plan view of one of the wings of an aeroplane of the tail-less type, with the control surface mounted thereon;

Fig. 2 is a front View corresponding to Fig. l but showing diagrammatically the control surface in its raised or operative position;

Figs. 3 to '7 are diagrammatic plan views of modified control surfaces, all of which are asymmetrical about their axes; but all of which have a common feature of the front portion descending through the wing and the rear portion upwards;

Fig, 8 is a diagrammatic end view of a further variation in which the control surface is divided in active position;

Fig. 9 is a diagrammatic plan View of a control surface which is symmetrical or substantially symmetrical about its axis;

Fig. 10 is a plan view of an aeroplane of the tail-less type and shows a control surface of one constructional form mounted on one of the wings and a control surface of another constructional form fitted to the other wing.

In the constructional form of the invention shown in Fig. 1 as applied to an aeroplane of the tail-less type having swept-back wings, each wing l is provided with a control surface 2 (hereinafter called a burbler) which is pear-shaped in plan and each burbler is pivotally arranged in a similarly-shaped orifice 3 formed towards the tip 4 of the wing. Each burbler is partially balanced about a forwardly directed axis A-B which is arranged at a suitable angle C (e. g. of from 45 to 70) to the line of flight XX of the aircraft or to the longitudinal axis thereof, the burbler axis AB in this instance being conveniently inclined upwardly from its inner end to its outer end as regarded from the front and as shown in Fig. 2 although of course, in front elevation this axis may take any angle as desired.

Each burbler is also asymmetrical in plan, the portion forward of the axis being of greater area than the portion aft of the axis. There is thus a kind of large curved bulge 5 on the forward portion adjacent to the tip of the wing and at the extreme span of the burbler, the after portion of the latter having a much smaller bulge 6 substantially opposite to the said larger bulge. Each burbler is mounted so as to be turnable from the position, see Fig. 1, in which it lies in and across the orifice 3 in the wing up to the extreme position in which it is at right angles tothe chord, as shown in Fig. 2, or even at a greater angle, for example 100. Owing to the inclination of the axis, the large bulge 5 on the forward portion describes an arc which is downward and rearward whilst the bulge on the rear portion describes an are which is upward and forward. A convenient lateral spacing for the area centre of each burbler is about three quarters of the wing span reckoned from the root end or from the adjacent side or the level of the adjacent side of the fuselage if the wing is a continuous, noninterrupted wing.

It will be appreciated that when the burbler is turned on its axis, the airstream is diverted from the high pressure area under the wing to the low pressure area above it, through the orifice formed in the wing when the burbler is turned. Such a control surface is bound to be I effective in COlll'ltEI'i'fl? any tendency of the air-- craft to spin, the pressure on the burbler is in creased and concentrated whilst control about all axes should be possible at much greater than critical angles without alteration (to any large.

extent) of the centre of pressure, thus maintaining horizontal attitude longitudinally. Further, pressure is built up gradually and symmetrically, increasing drag Without undue torsion or critical moments.

In the modified constructional form of the in-- vention shown in Fig. 3, also applied to an aeroplane of the above mentioned type, the burb-ler is pear-shaped in plan but in this construction the inner end i of the burbler is much narrower than that of the preceding construction. The inner end of the burbler also terminates much closer to the leading edge 8 of the wing.

The modified construction of burbler shown in Fig. 4 has its turnable axis AB arranged at a very slight angle only to the leading edge 8 of the wing. In this construction, the forward edge 9 of the burbler is practically straight. whilst the trailing edge I is only slightly curved at H but more steeply at E2 adjacent to the tip of the wing. It will also be observed from the figure that the burbler is asymmetrical about the axis A-B as viewed in plan.

The burbler shown in Fig. differs very considerably in shape from any of the other burblers described above. The burbler is asymmetrical about its turnable axis A--B and its leading edge mainly consists of a straight part l3 whilst its trailing edge is made up of .a slightly inwardly-curved part i4 and a straight part it, the latter and the part l3 being connected together by a curved end portion 16 adjacent to the tip of the wing.

In the construction shown in Fig. 6, the leading and trailing edge comprise, respectivel substantially straight portions El .and !8, the portion it being almost parallel to the turnable axis A-B whilst the portion I8 'is arranged at a greater angle to the axis. 7 The inner ends of the two edges are joined by a curved part 55 and the outer ends by a curved part 20.

In the construction shown in Fig. 7, the burbler somewhat resembles that shown in Fig. .6, except that the leading edge 2! and the trailing edge 22 are joined by an outwardly-bulged part 23. The burbler shown in Fig. 7 is also squatter than that shown in Fig. 6.

The modified control surface shown in Fig, 9 differs from the preceding control surfaces in that it is symmetrical about its turnable axis or substantially so, the leading edge 33 and the trailing edge 36 each being curved almost to the same radius. The inner end 35 of the control surface is almost pointed whilst the outer end is well rounded.

The burblers (of any of the kinds described above) .are arranged to be operated either independently or simultaneously, for example, by means of a single steering wheel operatively connected to a swing bar, each end of which is connected to a two-part push-pull rod to a lever carried on a turnable shaft. The latter is connected by rods, accommodated in the wing, to a lever which is linked to a lever extending from the under surface of the burbler. In order to allow the burblers to be operated independently or simultaneously, a compression unit (or other idle, action means) is arranged to connect the two parts of each of the push-pull rods connected to the swing bar. The steering column, or. wheel mounting, is also arranged in such a manner that it can be hinged bodily in a fore and aft direction, thereby moving the swing bar in the same direction and without being turned about its axis. This movement causes both burblers to be raised or lowered, as the case may be. On the other hand, the steering wheel and the mechanism connecting the same to the swing bar is so mounted hat the wheel is capable of turning relatively to the wheel mounting and of pivoting the swing bar about its axis. In this manner, only one of the two burblers is actuated, the other remaining in its inoperative position. Additional safety means (e. g. provided for ensuring that the burbler shall return to its inoperative position in the event of the failure of one of the, compression units.

In the further modified construction shown in Fig. 8, the burbler is divided in its action. That is to say, either part 24 or 25 of the burbler on either side of the axis 26 may be operated whilst the other part remains stationary or one part may be operated in advance of the other part. If the burbler is thus arranged it will be possible, if desired, to fold it backwards or forwards so that either the front or the rear half of the orifice in the wing i will be uncovered.

' Fig. shows two constructional forms of burblers fitted to the wings of a tail-less aeroplane. The two different constructions of burblers are only shown on the figure to illustrate the positioning of the burblers on the wings. It will be understood, of course, that the two burblers fitted on the same aeroplane would normally be the same in construction.

The air flow takes place through the wing past the front and back of the control surface from below to above, i. e. from the high pressure area under the leading edge to the low pressure area at the rear of the top of the wing. The steeper the flight path, i. e. the greater the angle of attack of the wing, the greater the diiference in pressure becomes and consequently the faster must be the flow of the 'airstream through the orifice in the wing and past the control surface. Thus, the worse the stalling tendency the more the inclination for the control surfaces to equalize pressure distribution. The problem of steep descent is not one of lift but of stable equilibrium and control of balance whilst lift is being reduced to a minimum. Even if vertical descent is attempted the control surfaces could not stall but must hold the aircraft about all axes of con trol.

Movements of the centre of pressure laterally, vertically and fore and aft can be definitely controlled and varied in different designs by suitable variation in the balance of the control surface about its axis, its symmetry, section, outline and curvature. For instance, particularly in the types shown in Figs. 3, 4 and 5, a definite increase of lift and forward movement of the centre of pressure may take place thus causing a. climbing angle during the first slight opening of the control surface. A subsequent larger opening of the control surface can, however, cause a loss of springs) may be lift and slight rearward movement of centre of pressure thus slightly putting the nose down and at the same time a loss of lift and steep flight path is taken up. Thus, with this type of control surface gradual and most accurate controlled variation of the lift-drag ratio for any given speed or angle of attack is made possible by the degree of opening and closing of the control surface and its nature relative to various types of design can be greatly varied insofar as its plan outline, position of axis, total area, and so on is concerned.

In the case of my invention the control surface will set obliquely inside the wing area in such a manner that the inequality of pressure between the top and bottom surfaces itself contributes to safe control, whilst pressure losses around the control surface are minimized. The variation in the values of lift and of drag and of the lift-drag ratio is possible under complete and fool-proof control of the pilot. This gives a safe balance about all axes in any weather conditions. The controllable variation in liftdrag ratio takes place without important change in the centre of pressure position except as may be desired by the control surface, because these changes are themselves dependent in inverse ratio to the speed of the aircraft and the air-- flow velocity through the orifice and past the control surface. The centre of pressure automatically adjusts itself to the centre of gravity movements to a very much greater extent than on known aircraft. For the same reason parasitic drag is absent and the control acts only in a manner required to produce the effect desired.

As regards the area of the control surface and its position on the wing, if the area of the control is too great in comparison with the: rest of the wing area, the loss of lift will be too great and dangerous and the relative increase of drag too much, thus causing loss of control and stability. If the area of the control is too small then the effectiveness and control and the liftdrag variation will be too weak and the object will be lost.

It is therefore suggested that one-third of the wing area will be about the maximum proportion for the area of the control surface, but this may be varied to suit individual needs. If the control surfaces are located too close to the centre of gravity they lose effect and must be of larger area. They can have some effect wherever placed, but most effect is probable when situated furthest from the wing root possible. Whether the surface is symmetrical or not is immaterial in principle, but has a different relative effect. It is essential that the lower leading edge should project below the wing surface and the upper rear edge above it, so that the airflow is directed as required and previously described on both sides of the control. The proportions of the surface in plan either in front or behind the axis is therefore to be determined by the prime features of design and performance aimed at for (a) the amount of drag required at different speeds (b) the amount of lift increase and decrease required at different speeds relative movements of the mean centre of pressure both fore and aft and vertically and laterally, because a larger surface in front of the axis than behind can result in a downward movement of the vertical centre of pressure (or a lowering of the mean centre of resistance) and vice versa. This can, of course, change the trim of the aeroplane. The actual area of the control on each side of the axis can affect the increase of drag and the relative lift variation. For example, see Fig. 4, a small area each side of the axis, and the axis at a maximum angle to line of flight causes a large variation in lift values, a considerable increase in lift when slightly open at high speed, but further opened, a rapid decline in lift with not very great increase in drag. Therefore, a fast and steep take-off and a fast and steep descent, but both needing more human control, since the control and the changes in lift-drag ratio are rapid and sensitive. On the other hand, a large area each side of the axis, and the angle of axis nearer 45 gives very little increase of lift accompanied by a bigger proportion of drag when slightly open and a rapid and very large increase or drag as more and more open, but with a, more slowly graduated loss of lift more firmly under control, giving a slow but fairly good climbing take-off, but a very slow and very easily controlled descent, steep or carefully regulated under simple and widely graduated liftdrag ratios.

The term aeroplane is of course intended to cover non-power driven and power-driven gliders and although the invention has been described above with reference to an aeroplane of the tail less type, to which the invention is particularly applicable, it is also applicable to aeroplanes having tales and to aeroplanes having the normal controls, viz. ailerons, elevators and rudders, and also to continuous, non-interrupted wings. The invention will be capable of development as a means of steepening the glide and increasing the take-off lift of heavy bombing or transport aircraft, and in particular it will lend itself to the improvement in the control, stability, gliding and climbing angle of sea-planes of the central hull or flying boat type, which would thus be able to dispense with the usual tail and control surfaces. The invention will also be found to be of considerable importance in the stabilizing of model aeroplanes and gliders, keeping them on an even keel and ensuring efficient directional, longitudinal and lateral control.

What I claim is:

1. Means for controlling an aeroplane in flight, comprising wing structure provided with an orifice adjacent each tip thereof and between the leading and trailing edges thereof, a control surface in each orifice and means for turning said surface, the latter being pearshapecl and asymmetrical in shape about its turnable axis as viewed in plan and having non-apertured outer surfaces and not greater in area than half the area of the wing and mounted in said orifice for turnable movement relatively thereto on a pivot axis which is directed forwardly and inclined to the longitudinal axis of the aeroplane at an angle less than 90 to said longitudinal axis, and said control surface also being so constructed and arranged that when turned from its inactive position, its leading edge can only project downwards and forwards towards the leading edge of the wing whilst its trailing edge projects rearwards and upwards, whereby air from the underside of the wing is caused to flow both over the top surface and over the underside of the control surface rearwards or mainly rearwards and upwards through the orifice in the wing thereby causing either a destruction of lift, pressure loss at the wing tip and negative pressure, or an increase of lift, according to the degree of opening of the orifice by the control surface and the relative velocity of the airstream caused to flow through the orifice and past the control surface, and thereby effecting a redistribution of pressure between the lower and upper wing surfaces through the orifice in which the control surface is disposed.

2. Means for controlling an aeroplane in fiight, comprising wing structure provided with an orifice adjacent each tip thereof and between the leading and trailing edges thereof, a control surface in each orifice and means for turning said surface, the latter being solid in construction and not greater in area than half the area of the wing and mounted in said orifice for turnable movement relatively thereto on a pivot axis which is directed forwardly and inclined to the longi tudinal axis of the aeroplane at an angle of from 45 to 70 to said longitudinal axis and said control surface also being so constructed and arranged that when turned from its inactive position, its leading edge projects downwards and forwards towards the leading edge of the wing whilst its trailing edge projects rearwards and upwards, whereby air from the underside of the wing is caused to flow both over the top surface and over the underside of the control surface-rearwards or mainly rearwards and upwards through the orifice in the wing thereby causing either a destruction of lift, pressure loss at the wing tip and negative pressure, or an increase of lift, according to the degree of opening of the orifice by the control surface and'the relative velocity of the airstream caused to fiow through the orifice and past the control surface, and thereby effecting a redistribution of pressure between the lower and upper wing surfaces through the orifice in which the control surface is disposed, and the approximate area center of each control surface being located on the wing structure at about threequarters of the span reckoned from the root end of the wing, whereby the control reaction of the control surface will have substantially a maxi-- mum effective moment arm about the fore and aft axis of the craft.

3. Means for controlling an aeroplane in flight comprising wing structure having an orifice therein at each side of the longitudinal axis of the aeroplane and. between the leading and trailing edges of the structure, a controlsurface pivotally mounted in each orifice and asymmetrical in shape about its pivotal axis as viewed in plan and having a continuous bounding surface,

each said control surface having an area less.

than half the adjacent area of the wing with said pivot axis directed forwardly and inclined to the longitudinal axis of the aeroplane at an angle less than to said longitudinal axis, and each said control surface being so constructed and arranged that when turned from its inoperative position the leading edge always projects downwardly and forwardly toward the leading edge of the wing whilst its trailing edge projects rearwardly and upwardly, whereby air from the underside of the wing is caused to flow over both the top and bottom sides of said control surface rearwardly or mainly rearwardly and upwardly through the orifice in the wing thereby causing either a destruction of lift, pressure loss at the wing tip and negative pressure, or an increase of lift, according to the degree to which the orifice is opened by the control surface and the relative velocity of the air stream caused to flow through the orifice and past the control surface, to thereby effect a redistribution of pressure between the lower and upper wing surfaces, said control sur- V faces being somewhat pear-shaped in plan and having their narrower ends directed towardsthe longitudinal axis of the aeroplane, each control surface as viewed in plan having a large curved bulge on the forward portion adjacent to the tip of the wing and at the extreme span of the control surface, and the after portion of the latter having a much smaller bulge substantially opposite to the said larger bulge.

4. Means for controlling an aeroplane in flight comprising wing structure having an: orifice therein at each side of the longitudinal axis of the aeroplane and between the leading and trailing edges of the structure, a control surface pivotally mounted in each orifice and asymmetrical in shape about its pivotal axis as Viewed in plan and having a continuous bounding surface, said control surfaces having an area less than halfthe adjacent area of the wing with said pivot axis directed forwardly and inclined to the longitudinal axis of the aeroplane at an angle less than 90 to said longitudinal axis, and each said control surface being so constructed and arranged that when turned from its inoperative position the leading edge always projects downwardly and forwardly toward the leading edge of the wing whilst its trailing edge projects rearwardly and upwardly, whereby air from the underside of the wing is caused to flow over both the top and bottom sides of said control surface rearwardly or mainly rearwardly and upwardly through the orifice in the wing thereby causing either a destruction of lift, pressure loss at the wing tip and negative pressure, or an increase of lift, according to the degree to which the orifice is opened by the control surface and the relative velocity of the air stream caused to flow through the orifice and pastthe control surface, to thereby effect a redistribution of pressure between the lower and upper wing surfaces, said control surfaces being somewhat pear-shaped in plan and having their narrower ends directed towards the longitudinal axis of the aeroplane, each control surface as viewed" in plan having a narrow forward portion extending rearwards for about onethird of the length of said surface, a large curved bulge on its trailing edge and a smaller curved bulge on its leading edge, the forward end of the pivot axis of the control surface being arranged relatively near to the leading edge of the wing.

5. Means for controlling an aeroplane in flight comprising wing structure having an orifice therein at each side of the longitudinal axis of the aeroplane and between the leading and trailing edges of the structure, a control surface pivotally mounted in each orifice and asymmetrical in shape about its pivotal axis as viewed in plan and having a continuous bounding surface, each said control surface having an area less than half the adjacent area of the wing with said pivot axis directed forwardly and inclined to the longitudinal axis of the aeroplane at an angle less than 90 to said longitudinal axis, and each said control surface being so constructed and arranged that when turned from its inoperative position the leading edge always projects downwardly and forwardly toward the leading edge of the wing whilst its trailing edge projects rearwardly and upwardly, whereby air from the underside of the wing is caused to fiow over both the top and bottom sides of said control surface rearwardly or mainly rearwardly and upwardly through the orifice in the wing thereby causing either a destruction of lift, pressure loss at the wing tip andnegative pressure, or an increase of lift, according to the degree to which the orifice is opened by the control surface and the relative velocity of the air stream caused to flow through the orifice and past the control surface, to thereby effect a redistribution of pressure between the lower and upper wing surfaces, said control surfaces being somewhat pear-shaped in plan and having their narrower ends directed towards the longitudinal axis of the aeroplane, each control surface as viewed in plan having a substantially straight leading edge arranged relatively near to the leading edge of the wing and at a slight angle only thereto and a slightly-curved trailing edge, a steep curve connecting the leading and trailing edges adjacent to the tip of the wing.

6. Means for controlling an aeroplane in flight comprising wing structure having an orifice therein at each side of the longitudinal axis of the aeroplane and between the leading and trailing edges of the structure, a control surface pivotally mounted in each orifice and asymmetrical in shape about its pivotal axis as viewed in plan and having a continuous bounding surface, each said control surface having an area less than half the adjacent area of the wing with said pivot axis directed forwardly and inclined to the longitudinal axis of the aeroplane at an angle less than 90 to said longitudinal axis, and each said control surface being so constructed and arranged that when turned from its inoperative position the leading edge always projects downwardly and forwardly toward the leading edge of the wing whilst its trailing edge projects rearwardly and upwardly, whereby air from the underside of the wing is caused to flow over both the top and bottom sides of said control surface rearwardly or mainly rearwardly and upwardly through the orifice in the wing thereby causing either a destruction of lift, pressure loss at the wing tip and negative pressure, or an increase of lift, according to the degree to which the orifice is opened by the control surface and the relative velocity of the air stream caused to flow through the orifice and past the control surface, to thereby effect a redistribution of pressure between the lower and upper wing surfaces, said control surfaces being somewhat pear-shaped in plan and having their narrower ends directed towards the longitudinal axis of the aeroplane, each control surface as viewed in plan having a leading edge which mainly consists of a straight part and a trailing edge made up of a slightly inwardly-curved part and a straight part, the latter and the leading edge being connected by a curved end portion adjacent to the tip of the wing.

7. Means for controlling an aeroplane in flight comprising wing structure having an orifice therein at each side of the longitudinal axis of the aeroplane and between the leading and trailing edges of the structure, a control surface pivotally mounted in each orifice and asymmetrical in shape about its pivotal axis as Viewed in plan and having a continuous bounding surface, each said control surface having an area less than half the adjacent area of the wing, with said pivot axis directed forwardly and inclined to the longitudinal axis of the aeroplane at an angle less than 90 to said longitudinal axis, and each said control surface being so constructed and arrarged that when turned from its inoperative position the leading edge always projects downwardly and forwardly toward the leading edge of the wing whilst its trailing edge projects rearwardly and upwardly, whereby air from the underside of the wing is caused to flow over both the top and bottom sides of said control surface rearwardly or mainly rearwardly andupwardly through the orifice in the wing thereby causing either a destruction of lift, pressure loss at the wing tip and negative pressure, or an increase of lift, according to the degree to which the orifice is opened by the control surface and the relative velocity of the air stream caused to flow through the orifice and past the control surface, to thereby effect a redistribution of pressure between the lower and upper wing surfaces, said control surfaces being somewhat pear-shaped in plan and having their narrower ends directed towards the longitudinal axis of the aeroplane, each control surface as viewed in plan having substantially straight leading and trailing edges, the leading edge being substantially parallel to the pivot axis of the control surface and the trailing edge being arranged at a greater angle to said axis and curved parts joining said leading and trailing edges.

8. Means for controlling an aeroplane in flight comprising wing structure having an orifice therein at each side of the longitudinal axis of the aeroplane and between the leading and trailing edges of the structure, a control surface pivotally mounted in each orifice and asymmetrical in shape about its pivotal axis as viewed in plan and having a continuous bounding surface, each control surface having an area less than half the adjacent area of the wing with said pivot axis directed forwardly and inclined to the longitudinal axis of the aeroplane at an angle less than 90 to said longitudinal axis, and each said control surface being so constructed and arranged that when turned from its inoperative position the leading edge always projects downwardly and forwardly toward the leading edge of the wing whilst its trailing edge projects rearwardly and upwardly, whereby air from the underside of the wing is caused to fiow over both the top and bottom sides of said control surface rearwardly or mainly rearwardly and upwardly through the orifice in the wing thereby causing either a destruction of lift, pressure loss at the wing tip and negative pressure, or an increase of lift, according to the degree to which the orifice is opened by the control surface and the relative velocityof the air stream caused to flow through the orifice and past the control surface, to thereby effect a redistribution of pressure between the lower and upper wing surfaces, said control surfaces being somewhat pear-shaped in plan and having their narrower ends directed towards the longitudinal axis of the aeroplane, each control surface as viewed in plan having substantially straight leading and trailing edges, the leading edge being substantially parallel to the pivot axis of the control surface and the trailing edge being arranged at a greater angle to said axis and curved parts joining said leading and trailing edges, and wherein the forward ends of the leading and trailing edges of each control surface are joined by an end part which is only slightly curved outwardly.

9. Means for controlling an aeroplane having a wing and a body structure in flight comprising control surfaces pivotally mounted in orifices in the wing structure adjacent the tips thereof and between the leading and trailing edges thereof, with the pivot axis of the surface extending at an angle with respect to the longitudinal axis of the plane of more than about 45 and less than about 70, said surfaces each corresponding in its transverse cross-section to the surface contour of the wing at the location of the orifice and being substantially pear-shaped in plan, said surfaces being movable so that their leading edges project downward only, and actuating means for selectively, individually or jointly moving the control surfaces so that each leading edge when in actuated position always extends downwardly and forwardly with respect to the wing.

10. Means for controlling in flight an aeroplane including a wing having orifices formed therein adjacent the tips thereof and a body structure; comprising control surfaces each surface including two relatively movable parts pivotally mounted on a common pivot in each orifice in the wing structure adjacent the tips thereof and between the leading and'trailing edges thereof, with the pivot axis of the surface and its parts extending at an angle with respect to the longitudinal axis of the plane, one part of each surface extending above and another part thereof extending below the wing structure, each 'part being so arranged that it cannot move through the orifice to the other side of the wing, the parts of said surfaces being relatively movable so that their extreme outer edges may project forwardly or rearwardly, and actuating means for selectively, individually or jointly moving the parts of the control surfaces so that their outer edges when in actuated position may extend forwardly or rearwardly with respect to the pivot.

HUBERT LEWELLEN PITT. 

